Introduction of metal impurity to change workfunction of conductive electrodes

Abstract

Semiconductor structures, such as, for example, field effect transistors (FETs) and/or metal-oxide-semiconductor capacitor (MOSCAPs), are provided in which the workfunction of a conductive electrode stack is changed by introducing metal impurities into a metal-containing material layer which, together with a conductive electrode, is present in the electrode stack. The choice of metal impurities depends on whether the electrode is to have an n-type workfunction or a p-type workfunction. The present invention also provides a method of fabricating such semiconductor structures. The introduction of metal impurities can be achieved by codeposition of a layer containing both a metal-containing material and workfunction altering metal impurities, forming a stack in which a layer of metal impurities is present between layers of a metal-containing material, or by forming a material layer including the metal impurities above and/or below a metal-containing material and then heating the structure so that the metal impurities are introduced into the metal-containing material.

1. A method of changing workfunction of a conductive stack comprising:
 providing a material stack that comprises a Hf-based dielectric having a dielectric constant of greater than silicon dioxide, a metal-containing material including at least one metal selected from Ti, Zr, Hf, V, Nb and Ta located above said Hf-based dielectric, and a conductive electrode located above said metal-containing material; and 
 introducing at least one workfunction altering metal impurity into said metal-containing material, wherein said at least one workfunction altering metal impurity is introduced during forming of a metal impurity containing layer or after formation of a layer containing said metal-containing material, and said introducing is selected from 
 (i) codepositing the at least one workfunction altering metal impurity and the metal-containing material, 
 (ii) forming a first layer of the metal-containing material, forming a layer containing the metal impurities on said first layer, and forming a second layer of the metal-containing material, and 
 (iii) forming a material layer containing the metal impurities below and/or above the metal-containing material, and subjecting the material stack to a thermal process, 
 
     and with the proviso that when an n-type workfunction is required, the at least one workfunction altering metal impurity comprises at least one element from Groups IIIB, IVB, or VB of the Periodic Table of Elements, and when a p-type workfunction is required the at least one workfunction altering metal impurity comprises at least one element from VIB, VIIB or VIII of the Periodic Table of Elements.